Knautia - Mars Midget Dying Out

I live near Madison, WI, and every year my Knautia mars Midget blooms non-stop from spring until NOW. Every July the middle of the plant starts to turn brownish/gray, and the leaves eventually all die. I cut back the plant to see if it will rebloom, but it doesn't. What is happening with the plant, and what can I do, so that the plant doesn't continue this yearly die out. Thank you, Unhappy Bucky Gardener